There are numerous applications in which spray polyurethane foam is used at a site for any number of applications in, but the most traditional use in the building trades is as a source of insulation. The Department of Energy reports that every year the average home wastes up to 40% of the energy used for heating and cooling as air moves through gaps, penetrations, and cracks in the exterior shell of the house, also known as the building envelope. Spray foam insulation is gaining in popularity because of its many benefits over conventional fiberglass insulation. Spray foam is able to fill in cracks and crevices which are too small for fiberglass insulation. The seamless application of the spray foam eliminates air infiltration, which reduces energy waste. Polyurethane spray foam insulation acts as a sound insulator, reduces vibration, and improves the indoor air quality. Also, polyurethane has the highest resistance to heat transfer, called R-value, per thickness of any common insulating product. Polyurethane spray foams are also moisture, mold, fungus, and insect repellant.
When using insulation, two factors are considered important: the resistance to heat transfer (R-value); and the ability to act as an air barrier. A high R-value indicates heat will travel slowly through the material. A low R-value indicates heat will travel quickly through the material. R-value is calculated by a formula that considers the thermal conductivity, k, and the thickness of the material. It is essential to consider the thickness of the material because a very thick material with a very high R-value over the total thickness, might have a lower R-value per unit than a very thin material with an average R-value. Closed cell polyurethane foam insulation has the highest R-value per thickness of any common insulating material.
The ability of the insulation to act as an air barrier is also critical. Pressure differences between the inside and outside of an enclosure cause air leakage to occur. Differences in pressure can be caused by many environmental factors such as temperature differences and wind. Air leakage contributes to warm air leaving an insulated area and cold air entering the area and can occur through cracks, gaps, openings, or through porous walls and insulation. An ideal insulation will minimize air leakage, keeping the warm air inside and the cold air outside of the insulated enclosure. Polyurethane foam insulations act as an air tight barrier, significantly lowering air infiltration.
The polyurethane foam insulation for such in-situ applications is typically supplied as a one-component froth foam or a two-component froth foam. A one-component foam means both the resin and isocyanate for the foam are supplied in a single pressurized container and dispensed from the container through a valve or gun attached to the container.
A two-component “froth” foam means one component is supplied in one pressurized container, typically the “A” container (i.e., polymeric isocyanate, fluorocarbons etc) while the resin is supplied in a second pressurized container, typically the “B” container (i.e., polyols, catalyst, blowing agents, flame retardants etc.). There are advantages and disadvantages to one-component and two-component foams. One advantage of the two-component system is its relatively long shelf life resulting from the fact that the chemicals are not mixed until they encounter one-another in the dispensing gun. This invention relates to two-component foams.
Typically two-component kits use pressurized cylinders about 7½″ in diameter, containing 1-5 gallons (10-50 pounds) which are connected by hoses to a dispensing gun. The two components of the foam are combined in the dispensing gun, and applied directly to the surface being insulated. When the two components combine, an exothermic reaction takes place allowing the gases in the froth to expand, forming small bubbles which become trapped in the mixture. Time must be given to allow the foam to cure and harden, giving it the ability to support itself. The volume of the foam expands as it cures, the amount of expansion that occurs is controlled by the formula of the foam being used. Polyurethane foam has natural adhesive qualities which allow such foams to bond strongly to any number of substrate surfaces.
As the foam cures, the gas bubbles trapped in the foam cause the pressure within the mixture to fall below that of the environment it is in. As air from the environment enters the mixture the pressure within the foam is restored to the levels of its surrounding, causing the foam to harden from the outside towards the surface it is applied to. As the foam hardens the R-value increases until it is completely cured. The time this process takes, as well as the final density of the foam varies with the specific formula of the foam being used.
Polyurethane froth foam reacts with water, and therefore must be applied only to dry surfaces. Humidity within the environment in which the foam is being applied should also be considered. The presence of high humidity in the environment or moisture on the surface being sprayed degrades the adhesion of the foam to the surface, disrupting the complete bonding to the desired surface and allowing the foam to be easily peeled off the wall. Cold temperatures have the same affect on the foam, causing the moisture on the substrate to freeze into ice crystals, disrupting bonding to the desired surface. The surface being sprayed and the ambient temperature must be of a minimum temperature that varies with the formula of the foam and the dispensing system being used to apply the foam. The technical data sheet for a popular polyurethane spray foam that is commonly used in the industry currently specifies the spray foam only be applied between temperatures of 50° F. and 110° F.
Variations of the elements of spray foam application systems are known in prior art. Examples of two-part foam dispensing guns can be found in Fomo Products, Inc.'s U.S. Pat. No. 4,550,863; Fomo Products, Inc.'s U.S. Pat. No. 5,242,115; Fomo Products, Inc.'s U.S. Pat. No. 5,429,308; and Fomo Products, Inc.'s U.S. Pat. No. 6,345,776. Examples of a nozzle for a two-part foam dispensing gun can be found in Fomo Products, Inc.'s U.S. Pat. No. 6,840,462. Spray foam polyurethane insulation are also commercially available, for example DOW Chemical's SPF insulation system, however the system of this invention contains numerous performance improvements over current commercially available systems such as increased application rates and the ability to be utilized under a broader range of environmental factors. To date the elements of the system of this invention as well as the extra features incorporated into this invention have not been combined to find a solution to the industry need for a portable, rapid system for insulating desired surfaces in the harsh construction environment which allow a two-component foam to be applied at temperatures lower than 50° F., certainly lower than 32° F., and more preferably at temperatures as low as 20° F. without peeling.